Look closely at the two scale-eating cichlid fish Perissodus microlepis
above. See how their mouths are slightly asymmetric? For example, the
mouth of the fish on the left curves slightly to the right. That, translates
to handed foraging behavior:

... an asymmetric ‘left’ mouth morph preferentially feeds
on the scales of the right side of its victim fish and a ‘right’
morph bites the scales of the left side. This species has therefore
become a textbook example of the astonishing degree of ecological specialization
and negative frequency-dependent selection. We investigated the strength
of handedness of foraging behavior as well as its interaction with morphological
mouth laterality in P. microlepis. In wild-caught adult fish we found
that mouth laterality is, as expected, a strong predictor of their preferred
attack orientation.

So, despite having no hands, fish can be left- or right-"handed" (or perhaps, left- and right-finned!)
Now you know.